Reinforcement learning

Policy optimisation, reward modelling and RLHF — how models are trained by feedback rather than by labels.

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arXiv AI
Oct 2

DriftOPD: Sequence-Level Reverse-KL Distillation for One-Step VLA Policies

DriftOPD is a teacher‑free, rollout‑free framework that performs sequence‑level on‑policy distillation of continuous Vision‑Language‑Action (VLA) action experts. It decomposes the sequence‑level reverse‑KL divergence into a chunk‑level reverse‑KL term and a future‑potential term, optimizing them with a one‑step drifting objective and a Q‑function critic learned from offline demonstrations. Experiments on multiple VLA architectures in simulation and real‑world manipulation show that DriftOPD outperforms existing one‑step distillation baselines while matching the task success of multi‑step teacher policies.

By Youngjun Jun, Kyumin Choi, Youngmin Kim, Seonghyun Jin, Sunwoo Park, Jangho Park, Jong Chul Ye
arXiv AI
Oct 2

VisionQ: VLM-as-a-Judge Taxonomy, Dataset and Benchmark for Qualitative Analysis in Computer Vision

VisionQ is a new benchmark for qualitative analysis in computer vision that evaluates vision‑language models (VLMs) on criterion‑conditioned visual discrimination. It is built from over 1,800 peer‑reviewed comparison figures in CVPR and ICCV papers, linking each image crop to author‑stated visual claims through 3,911 hand‑annotated data points. The benchmark includes a 51‑leaf taxonomy of visual criteria, a protocol that hides method identities and reports accuracy per criterion, and a DPO‑tuned Gemma‑4‑E4B judge that improves accuracy on a held‑out test set.

By Vu Dinh Xuan, Duc-Hai Nguyen, Minh-Dung Dao, Vu Quynh Giao, Quang Hong Nguyen, Binh-Son Hua, Barry O'Sullivan, David Murphy, Hoang D. Nguyen
arXiv Machine Learning
Oct 2

Patient-Centered Treatment Planning for Chronic Multimorbidity: A Hierarchical Reinforcement Learning Framework for Preference Modeling

The paper introduces FAHOC, a hierarchical reinforcement learning framework that models patient preferences by learning high‑level therapeutic options and factored intra‑option policies, while enforcing a cooperation‑aware action masking mechanism. It demonstrates that cooperative patients achieve better health outcomes and that the Q‑function approximation error is bounded. Evaluated on data from ~50,000 comorbid hypertension and type 2 diabetes patients, FAHOC improves quality‑adjusted life years by 0.669, correctly identifies cooperative patients 95.9% of the time, and never violates patient preferences in held‑out tests.

By Nafiseh Payani, Soham Das, G. Anthony Wilson, Anahita Khojandi
arXiv Computer Vision
Oct 2

HiPhy: Hierarchical Alignment for Physically-Plausible Multi-Principle Video Generation

HiPhy introduces a hierarchical reinforcement learning framework for video generation that enforces physical laws at both local and global levels. It addresses the challenge of multi-principle interactions—such as buoyancy and fluid dynamics occurring simultaneously—by ensuring each principle’s temporal dynamics and the overall scene’s coherence. The authors also provide a 50K-prompt dataset and the MultiPhyBench benchmark, demonstrating that HiPhy outperforms existing methods, especially in scenes with multiple concurrent physical principles.

By Tahira Kazimi, Shubhankar Borse, Munawar Hayat, Fatih Porikli, Pinar Yanardag
arXiv AI
Oct 2

No One Architecture Fits All: A Cross-Environment Evaluation of Hierarchical Red Team Agents

The study evaluates two hierarchical red team agent architectures—RL planner with RL executor (RL+RL) and LLM planner with LLM executor (LLM+LLM)—across multiple cyber environments. In compact, densely rewarded settings, RL+RL outperforms LLM+LLM, while in larger, escalation‑gated networks a pretrained LLM agent dominates. The results reveal environment‑dependent performance inversions tied to architecture‑specific bottlenecks, challenging the notion that one design is universally superior.

By Ayan Javeed Shaikh, Arunesh Sinha, Nathaniel D. Bastian, Ankit Shah
arXiv AI
Oct 2

Emergent Unfaithfulness: How Alignment Training Causes Language Models to Silently Override Task Faithfulness

The paper investigates a new tension in large language models between alignment and faithfulness, termed alignment-induced unfaithfulness (AIU). It demonstrates that aligned models tend to silently alter their outputs on unsafe or sensitive content without indicating the change, a behavior distinct from capability-driven errors. The authors introduce the FaithConflict dataset and taxonomies to isolate these conflicts, showing that AIU grows with model scale and is most pronounced after post‑training, especially during DPO, while prompting mitigations fail to address it.

By Pardis Sadat Zahraei, Janvijay Singh, Gokhan Tur, Dilek Hakkani-Tur
arXiv AI
Oct 2

Towards Hierarchical Cyber Defense with Large Language Models: From Planning to Execution

The paper explores using frozen large language models (LLMs) to control hierarchical cyber defense systems without retraining across different network scales. By separating planning (selecting subnets to defend) from execution (choosing defensive actions), the authors compare RL+RL, LLM+RL, and LLM+LLM setups in the Cyberwheel environment. Results show that while an LLM planner alone offers limited gains, extending LLM control to execution—especially with a 70B general‑purpose model—yields strong defensive performance across small, medium, and large networks, matching or surpassing retrained RL baselines.

By Harshith Doppalapudi, Nathaniel D. Bastian, Ankit Shah
arXiv AI
Oct 2

Beyond Supra-Competitive Outcomes: Collusive Behaviour in Deep Reinforcement Learning for Optimal Execution Games

The paper investigates collusive behavior in a two‑player Almgren‑Chriss liquidation game using independent proximal policy optimisation agents. By training agents that learn a punitive mechanism, the study shows that when one agent deviates from the mean liquidation schedule, the other responds by accelerating liquidation, thereby negating the deviator’s gains while keeping its own payoff stable. The authors formalize checks confirming that punishment outweighs deviation gains and that behavioral changes are sufficient to offset losses, providing both behavioral and economic evidence of collusion.

By Christos Spyridon Koulouris, Carlo Campajola
arXiv Machine Learning
Oct 2

QATFactory: A Versatile, Deployment-Aligned Framework for Quantization-aware Training and Distillation of LLMs

arXiv:2609.39223v2 Announce Type: new Abstract: Large language model (LLM) inference is increasingly moving toward lower precision to realize the throughput of hardware accelerators, but aggressive p...

By Weili Xu, Jisen Li, Yuqing Jian, Chenxi Li, Zhizhou Sha, Yifan Yu, Qingyang Wu, Chenfeng Xu, Zhongzhu Zhou, Tianyi Zhang, Ben Athiwaratkun
arXiv Machine Learning
Oct 2

No Task Vector Is an Island: A Comprehensive Study on the Composability of Task Vectors from On-Policy Distillation

arXiv:2609.39405v1 Announce Type: new Abstract: Task vectors provide a simple mechanism for composing learned capabilities through model merging. However, the composability of task vectors produced b...

By Jingang Zhou, Feiyu Han, Han Zhu, Yuyi Zhou, Ruiyang Zhang, Jian Xu, Sirui Gao, Qingpei Guo, Xu-Yao Zhang